Silicon wafers have traditionally been processed in stages such as deposition, oxidation, and etching, for example, in batches of twenty to forty wafers at a time. The batches are processed inside quartz tubes wherein the wafers are held separately on quartz "wafer carriers". The tubes and wafers are heated by furnaces to a temperature ranging from about 800.degree. C. to about 1200.degree. C. Typically these furnaces are resistance heated furnace structures, such as furnaces heated with electric metal coils, and have processing times of several hours.
Single wafer processes have recently been developed. Instead of long tubes with wafer carriers, smaller chambers are used, and the time for processing one wafer can be on the order of one minute. One of the most prevalent single wafer processes uses a quartz chamber and is referred to as a rapid thermal process (RTP). RTP and other similar single wafer processes still heat the wafers from about 1000.degree. C. to 1200.degree. C.; however, tungsten halogen lamps are used instead of resistive heating. Some batch processes likewise use tungsten halogen lamps instead of resistive heating. Such processes are generally referred to as "fast batch processes" because they require more time than single wafer processes but less time than traditional batch processes.
Conventional RTP systems for semiconductor manufacturing use the tungsten halogen lamps to rapidly heat single silicon wafers laying horizontally within quartz parallel-plate reactors. In such systems, efficiency is compromised because the spectral emittance of tungsten lamps is skewed toward the infrared region (where silicon absorption is low) and because the heat irradiated by the hot silicon surfaces is transmitted through the reactor walls and lost outside the reactor. In addition to requiring a large amount of electric power for the above reasons, heating variations across the wafers are caused by the relative position of the wafers with respect to the lamps.